Dual signal guidance system for the blind



- .Filed Feb. 14, 1966 Feb. 10,-1970 s I I. uAHAs 3, 3

DUAL SIGNAL GUIDANCE SYSTEM FOR THE BLIND I 2 Sheets-Sheet 2 3| I I I I 3| 33 -v f-+- I FIG.3 AI,3O

Tl INVENTOR SELIM A, NAHAS ATTORNEY 5 United States Patent Int. Cl. G08g 1/00;r104b 5/00; G01r 19/00 US. (:1. 340-32 6 Claims ABSTRACT OF THE DISCLOSURE A guidance system particularly adapted for guiding the blind comprising means to generate modulated signals of different audio frequencies and to amplify and transmit these signals along conductors for each frequency; a receiver mounted in a cane adapted to selectively or jointly receive the varied frequency signals; said receiver comprising oscillating means responsive to each signal, means to amplify the signals thereby giving an indication to each of a plurality of persons carrying such receivers of thir respective coordinates in a conductor framework.

The present invention relates, in general, to guidance systems and, more particularly, to guidance systems which will enable a blind person to find his way in any given area such as a building, a park, a town, or a city. More particularly, the guidance system of the present invention is based on communicating to a blind person his particular location at any given point within a given area, through signals transmitted to the blind person by means of a strong audio frequency electromagnetic induction field.

It is an object of the present invention to provide a guidance system for blind persons which is not only simple and economical to manufacture, install, and use, but is also reliable in operation.

It is another object of the present invention to provide a guidance system for the blind which can be standardized and made applicable to many different locations.

It is a further object of the present invention to provide a guidance system for the blind which requires a minimum of training to use and which can be used by an unlimited number of persons.

Other objects of the present invention will become apparent from the following description, the accompany ing drawings, and the claims.

The guidance system according to the present invention comprises at least two tone generators each of which is capable of generating a signal of different frequency in the audio frequency range; means of modulating the signals in a predetermined sequence; electromagnetic induction field generating means including conductors extending from each transmitter through the area to be served by the guidance system; means for amplifying the modulated signal produced by said tone generators to a high voltage level and applying the same to the conductors of each transmitter to generate an electromagnetic induction field along the conductors; a plurality of portable receivers each of which is adapted to selectively or jointly receive each of the different frequencies transmitted by said electromagnetic induction fields in the area served by the guidance system comprising electromagnetic oscillating means tuned to respond to each frequency transmitted; and means to amplify the signal received and to produce an audible signal modulated in the sequence of the modulation at the origin of the signal.

The guidance system of the present invention is further illustrated by the attached drawings, in which:

3,495,213 Patented Feb. 10, 1970 "'ice FIGURE 1 is a block diagram of a transmitting sysfjelrndembodying the present invention for guiding the FIGURE 2 is a block diagram of a receiver such as is suitably carried by the blind person, on a cane; and

FIGURE 3 is a simplified layout diagram illustrating the guidance system adapted to two intersecting streets.

Referring now to FIGURE 1 of the drawings, the guidance system of the present invention employs at least two transmitting stations 10 and 11 comprising tone generators capable of generating a signal in the audio frequency range, such as oscillators 12 and 13 which can be of conventional design.

The tone generators are designed to each produce a signal at a widely separated audio frequency which can be readily distinguished by the human ear. In addition, the transmitting stations contain means for modulating or interrupting the signals produced by each of the tone generators in a predetermined sequence such as, for example, Morse code. Such interruptors or modulators can be switches of the rotating drum type or pulse generators 14 and 15. The resulting coded signals are then suitably amplified by conventional amplifiers 16 and 17 to feed loops 18 and 19. It will be appreciated that the power output requirements of the amplifiers 16 and 17 will be selected in accordance with known engineering principles to provide a suitable high voltage output to feed loops 18 and 19, and to provide an electromagnetic field of sufiicient strength to be picked up by the receiver. The loops are arranged to intersect and thus can be employed to guide along paths in a plane, as well as to pinpoint locations by employing a high voltage audio frequency electromagnetic induction field which extends only a limited distance from the field generating cables or loop-s 18 and 19. Although the loops 18 and 19 are shown to be linear and intersecting at right angles, it will be apparent that such is not critical to the guidance system of the present invention and that non-linear loops can be employed as well as loops which intersect at angles other than right angles. It will be apparent that the transmitting stations are further not limited to producing a single coded signal in a single loop, but can be readily modified to feed differently coded signals in a repeating manner to a number of loops by synchronizing the coding of the signal with the activation of any particular loop. If necessary, more than two transmitting stations can be employed. All of the parallel loops will, of course, be on the same audio frequency to distinguish such over intersecting loops.

The guidance system receiver employed by the blind person to guide him is preferably transistorized and battery-operated so as to be compact and light, as well as portable. In a preferred embodiment, the receiver is divided into two parts and mounted on the cane 20 of the blind person, as illustrated in FIGURE 2 of the attached drawings. The lower unit 21 attached to the cane by means of clamp 22 contains two inductor circuits each of which is tuned to one of the frequencies emitted by the transmitters 10 and 11 and capable of receiving the signal on such frequency. The signals received by the two LC. circuits are transmitted by coaxial cables 23 to the remainder of the receiver located in container 24 containing the batteries acting as the power source for the amplifier, a transistorized amplifier of, for example, four transistors operatively connected to a loudspeaker or earphones, and two switches operable from the outside of the container and each capable of disconnecting one of the induction circuits. If desirable, an additional switch to disconnect the batteries is also incorporated into the container. The container is also mounted by clamps 25, or other means, to the upper extremity of the cane.

The above-described guidance system of the present invention is of particular value in guiding blind persons in any area which can be reduced to a rectangular coordinate or similar system having two principal intersecting axes. Thus, a city having a large proportion of its streets running in either the north-south or vertical direction, or the east-west or horizontal direction, can be transformed into a rectangular coordinate system by classifying the diagonal streets as either vertical or horizontal according to the smaller angle with the rectangularly intersecting streets.

The guidance system of the present invention is, however, not limited to the use of coordinate systems involving two rectangularly intersecting axes. Loops parallel to three or more axes can be employed, provided three or more tone generators are, employed emitting signals at different frequencies, and provided receivers are employed which are capable of receiving the number of frequencies emitted by the tone generators.

As illustrated in FIGURE 3, the cables and 31 emitting the guiding signal at the two frequencies are located along the center line of sidewalks 32 and 33, as well as pedestrian crossings 34 and 35, running up one side of the street and down the other, being connected to the transmitters T and T at the origin of the street and interconnected at the end of the street. Although it is possible to suspend the cable above the sidewalk, it is preferable that the cable be located in the ground and thus in close proximity to the induction circuits located, for example, on the lower extremity of a cane of a blind person. The transmitter T produces a signal at a frequency characteristic for vertical streets which is modulated to result in a coded signal assigned to V-Street, whereas the transmitter T produces a signal at a diflferent frequency characteristic for horizontal streets, in a code assigned to H-Street.

A blind person located, for example, on V-Str'eet at position A and proceeding towards the intersection of V- and H-Streets will receive a signal on his receiver in the audio frequency characteristic of vertical streets, in the code assigned to V-Street. Should he tend to stray from the center of the sidewalk, this would be indicated by a weakening of the signal. When he reaches point B at the intersection, both of the induction circuits in his receiver are activated and he receives the signals of both vertical and horizontal street frequencies coded to identify V- and H-Streets. The mixed reception will indicate that he is approaching an intersection. By disconnecting either induction circuit, he will be able to receive each signal separately and thereby locate himself at the intersection of V- and H-Streets. If, at this point, he wishes to cross the street, he will follow the signal emitted by cable 31, i.e. in a frequency assigned to horizontal streets and modulated in the code assigned to H-Street. Alternately, he can follow the mixed signals, turn the corner and proceed until he reaches point C, at which point he can cross H-Street by following the signal of cable 30, or continue to proceed along H-Street by following the signal of cable 31. A pocket guidebook in Braille will allow him to decode the signal and identify the particular street.

It will be appreciated that standardizing the distances in which both signals can be heard will aid the blind person in crossing a street or turning a corner. If the frequencies and the codes are selected in progressing order, it will be possible for a blind person having a single receiver to be guided in any area equipped with the guidance system of the present invention, and such a person would only require a simple guidebook which would translate the coded signals of the rectangular coordinate system to the traffic pattern of any given area. The guidance system of the present invention, additionally, can be used by an unlimited number of persons if equipped with the receivers of the type described. Additional modifications of the system described include separate transmitting stations to identify particular individual areas within the coordinate systems. The signals emitted from such transmitters may be on the same frequencies capable of being received by the described receiver employing a special code, or they can be on a third frequency within the audio frequency range and the receiver can be, accordingly, modified to transmit such signals to the user of the guidance system.

It is to be understood that although the present invention has been described with specific reference to particular embodiments thereof, it is not intended to limit the invention thereto, since changes and alterations therein may be made which are within the scope of the invention.

What is claimed is:

1. A guidance system particularly adapted to guiding the blind, comprising at least two tone generators each of which is capable of generating a signal of different frequency in the audio frequency range; means of modulating the signal; electromagnetic induction field generating means including conductors extending from each transmitter through the area to be served by the guidance system; means for amplifying the modulated signal produced by said tone generators to a high voltage level and applying the same to the conductors associated with each of the transmitters to generate an electromagnetic induction field along the conductors; at least one receiver operatively joined to said electromagnetic induction field, said receiver selectively or jointly receiving each of the different frequencies transmitted by said electromagnetic induction fields in the area served by the guidance system and comprising electromagnetic oscillating means tuned to respond to each frequency transmitted; and means to amplify the signal received and to produce an audible signal modulated in the sequence of the modulation at the origin of such signal.

2. The guidance system of claim 1, wherein the conductors of the electromagnetic induction field intersect.

3. The guidance system of claim 2, wherein the conductors of the electromagnetic induction field intersect at right angles.

4. The guidance system of claim 2, wherein modulat ing means capable of generating a plurality of different signals of the samefrequency along a plurality of conductors parallel to each other are employed.

5. The guidance system of claim 1, wherein the receiver includes transistorized, battery-operated amplifying means.

6. The guidance system of claim 1 wherein the receiver is mounted adjacent one extremity of a cane and wherein said receiver comprises an inductor circuit means tuned to each frequency of the transmitted signals, an amplifier for receiving the signals, a power source for said amplifier, a speaker operatively connected to said amplifier, said speaker being located adjacent the opposite extremity of the cane; and switching means adapted to activate said inductor circuit means to receive one or more signals.

References Cited UNITED STATES PATENTS 2,442,851 6/ 1948 Halstead 17982 3,162,726 12/ 1964 Rosenberg 179-82 3,175,047 3/1965 Borberg 17982 3,383,595 5/1968 Obata. 34032 2,791,762 5/ 1957 Berry.

FOREIGN PATENTS 229,356 2/ 1925 Great Britain.

THOMAS B. HABECKER, Primary Examiner U.S. Cl. X.R. 17982; 324-67 

